We have demonstrated increased concentrations of anti-I cold agglutinins in cancer sera, in particular in sera of patients with stage I-III breast carcinoma, and increased activities of Ii-antigens in sera of stage IV carcinoma. We plan to develop a RIA to quantitate anti-Ii activities and Ii-antigens in sera of individuals with various types of carcinoma, with an initial emphasis on breast carcinoma and individuals with possible pre-malignant breast lesions. Ii-active glycoproteins and oligosaccharides will be used in inhibition assays of anti-Ii in cancer sera to assess whether certain immunochemical determinants are preferentially expressed. Ii-antigens from cancer sera and tissue will also be studied by their ability to inhibit immunochemically characterized anti-Ii sera. The results of these studies will aid in our understanding of the relationship of the expression of anti-Ii agglutinins and Ii antigens to the development and progression of carcinomas.